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The Trump-endorsed American Health Care Act authored by House Speaker Paul Ryan will lead to millions more Americans being uninsured, according to a formal estimate released Monday by the Congressional Budget Office. The grisly assessment will further imperil legislation that is already being heavily criticized by other Republicans.

The CBO found that by next year, 14 million more people would be uninsured, rising to 24 million in 2026. In total, 52 million Americans would be uninsured by 2026 under the AHCA, compared to 28 million if the Affordable Care Act remains on the books.

This projection is far worse than expected. The Standard & Poor's rating agency had made a preliminary prediction last week that suggested the legislation would only lead to 6-10 million additional uninsured people in the United States.

Health insurance premiums would also rise in the short term: between now and 2020, single policyholders would find their health insurance premiums rising 15-20 percent over the current Obamacare law.

The Republican proposal would also drastically reduce the amount of money spent on low-income individuals who qualify to for Medicaid. CBO estimates that over the next decade, $880 billion less would be spent on this program and 14 million fewer people would be enrolled in Medicaid by 2026 — 17 percent less than under Obamacare.

Younger individuals, who would no longer face a mandate to purchase insurance, will be less likely to do so — making the mix of insured individuals older, on average.

And for those older enrollees in health insurance, premiums are likely to skyrocket. Under the AHCA, insurers would be allowed to charge older Americans five times more than younger ones, rather than three times under Obamacare. One example that the CBO gives is a 64-year-old person with an income of $26,500. Under current law, the individual's net premium is $1,700. Under the Republican proposal, the premiums would rise more than eight-fold to $14,600.

The legislation does come with a silver lining, especially for deficit hawks on Capitol Hill: the deficit would be decreased by $337 billion over the next decade.

The health care bill’s political prospects have come under attack over the past week in the GOP.

Sen. Tom Cotton, a Republican from Arkansas, told his House colleagues that they ought to make major revisions to the legislation before they send it to the Senate. “To my friends in House: pause, start over. Get it right, don't get it fast,” he tweeted. Arkansas is one of the states which embraced the expansion of Medicaid under Obamacare.

Other Republicans have criticized the legislation for leaving far too much of the Obamacare health care reforms in place.

Within an hour of the CBO report's release, Health and Human Services Secretary Tom Price told reporters, "We disagree strenuously," and pledged that the bill would actually cover more Americans at a lower cost. Price has offered no evidence of this yet.

The White House preemptively criticized the Congressional Budget office last week.